It is generally well-known that acoustic signals can be manipulated by converting them to electronic signals with a transducer, such as a microphone, and then altering those electronic signals before they are provided to a sound providing device, such as a speaker. For example, many stereos have an equalizer that can be used to enhance or suppress signals any of a number of desired frequency ranges. In some situations, it may be desirable to enhance or suppress certain features of an acoustic signal, but it may not be practical or desirable to accomplish such enhancement or suppression electronically. For example, as noted in the incorporated patent, in the case of a stethoscope, a medical practitioner may not want to run the risk of electronic problems or low batteries at an inconvenient time. Consequently, it would be desirable to be able to enhance and/or suppress aspects of acoustics signals in a non-electronic manner.